1. Technical Field
The disclosed embodiments generally relate to methods and systems for providing a variable capacitance to an electronic circuit.
2. Background
Switched capacitor banks are used in microelectronics for a variety of reasons. For example, a switched capacitor bank can be used to adjust the resonance of a tunable resonator, to alter the transfer function of or to tune a filter, or to match a load impedance of an amplifier.
A monolithically integrated switched capacitor bank using Micro Electro Mechanical System (MEMS) technology is described in U.S. Pat. No. 5,880,921. The capacitor bank includes a plurality of switch-capacitor pairs attached in parallel between a power line and a ground line. Each switch-capacitor pair includes a MEMS switch in series with a capacitor. Similar devices incorporating mechanical relays and field effect transistors instead of MEMS switches are also described therein.
The capacitance of a parallel plate system, where a dielectric medium is located between two electrodes, is determined by the following formula:
      C    =                            ɛ          0                ⁢                  ɛ          r                ⁢        A            d        ,where ε0 equals the free space permitivitty (i.e., 8.85418×10−14 F/cm), εr equals the relative permitivitty (i.e., the dielectric constant) of the dielectric medium, A equals the area of overlap between the top and bottom electrodes, and d equals the thickness of the dielectric medium between the two electrodes.
Based on the above formula, if a plurality of capacitors in a capacitor array are electrically connected in parallel this results in an increase in the overlap area of the electrodes, thus the capacitance associated with the connected capacitors may be substantially equal to the sum of the individual capacitances associated with each capacitor. Accordingly, if capacitors in a capacitor array can be controllably and separably connected, a variable capacitor can be produced.
What is needed is a method and system for providing an electronically variable capacitor array for supplying a variable capacitance.
The present disclosure is directed to solving the above listed problem.